Medical data show that a regular exercise leads to a healthier life. Exercise is important to maintaining a healthy lifestyle and an individual's wellbeing. Accordingly, many individuals want to participate in exercise programs. The fitness of the heart is the key to one's aerobic endurance—cardiovascular respiratory endurance. For health and racing reasons, aerobic endurance is a point of focus for almost any runner. Aerobic and anaerobic capacities reflect the condition of a subject's aerobic and anaerobic metabolisms, respectively. Aerobic metabolism refers to the body's method of producing energy by a process requiring oxygen. Whenever the available amount of oxygen-based energy fails to meet the demand, an anaerobic state occurs where energy is produced by a process that does not require oxygen, but may result in an oxygen debt. Thus, aerobic and anaerobic metabolisms are related but are separate functions.
It is of value to distinguish the aerobic metabolism energy sources from anaerobic metabolism energy sources. Muscles contract from the phosphorylation of adenine triphosphate (ATP). Metabolic energy sources replenish the ATP when sustained or repeated muscle contractions occur. Aerobic oxidative phosphorylation provides ATP at a steady rate until the energy reserves of glycogen or fatty acids have been depleted. At this point, or just prior to this point, anaerobic metabolism begins. Also, anaerobic metabolism is also called upon when a higher level of mechanical work is required. The anaerobic metabolism sources of ATP are less efficient, require more caloric energy to produce ATP, deplete sooner, and produce an oxygen debt.
Physical exercise is an important activity that many individuals undertake to maintain their physical fitness. It has been shown, for example, that physical fitness contributes positively toward maintaining healthy body weight; building and maintaining healthy bone density, muscle strength, and joint mobility; promoting physiological well-being; reducing surgical risks; and strengthening the immune system. Athletes and fitness buffs often monitor and record certain performance values while they train and exercise. For example, runners, bikers, and other athletes often track and record their distance, speed, pace, heart rate, and/or burned calories during a workout so that they can compare these performance values to benchmark values or to values from previous workouts. Historically, these performance values have been monitored and recorded with various different stand-alone components including stop watches, pedometers, heart rate monitors, and calorie calculators or charts. Those skilled in the art will appreciate the fact that the use of all these different components is time-consuming, cumbersome, and often inaccurate.
To alleviate some of these problems, portable personal training devices have been developed to simplify and improve exercise monitoring. Information about the individual's progress toward achieving their goals may be collected by using sensors that measure various physical and/or physiological parameters associated with the individual's physical activity. U.S. Pat. No. 7,828,697 relates to a portable personal training device including a location determining component operable to determine a geographic location of the device, where a housing having a first portion and a second portion coupled to the first portion at an angle, and a strap operable to secure the housing to a user's wrist such that the first portion is operable to be positioned on a top of the wrist and the second portion is operable to be positioned offset from the top of the wrist. Such a configuration facilitates both the wearing and the operation of the device. U.S. Pat. No. 7,789,802 provides a physical training device using GPS data to assist a user in reaching the user's performance goals and completing training sessions by tracking the user's performance, by communicating progress including progress relative to user-defined goals, by communicating navigation directions and waypoints, and by storing and analyzing training session statistics. U.S. Pat. No. 8,033,959 further provides a portable fitness monitoring system that includes: a portable fitness monitoring device; a sensor that communicates with the portable fitness monitoring device to sense the performance parameters during a physical activity conducted by the user and to communicate the performance parameter data to the dedicated portable fitness monitoring device; a music device directly coupled to the portable fitness monitoring device; and an audio output device directly coupled to the portable fitness monitoring device, wherein music is transmitted from the portable music device to the audio output device through the portable fitness monitoring device.
Although the above portable fitness monitoring devices have been provided, they only rely on heart rate as the main parameter without immediate analysis; meanwhile some use a fixed calculation table to cover all individuals but neglect health and environmental conditions. These devices fail to take personally physiological state, exercise types (such as aerobic and anaerobic exercises) and workout environmental conditions (such as temperature, humidity, altitude and air quality) into consideration. In view of the fact that physiological states, exercise types and environments can also contribute to a variation in heart rate, these devices overly simplify the fitness assessment or such an analysis is produced after the end of exercise. Thus a user cannot instantly and continuously realize the changes to his/her physical conditions and can only evaluate his/her performances based on his/her heart rate during an exercise. Therefore, there is still a need to develop an exercise status display and a coaching system that is capable of providing instant physical information so that a user can realize his/her current physical state and further decide which action (such as sprint, aerobic endurance or dynamic recovery) is to be taken next.